Julia Roberts Is Expecting Baby No. 3

Hazel and Finn will soon have to share their famous mom's attention: Julia Roberts is expecting her third child with husband Danny Moder.

Roberts is due this summer, her rep, Marcy Engelman, confirms exclusively to PEOPLE.

News of the pregnancy first appeared in the New York Post's Page Six column. Roberts, 39, and Moder, 37, were married in July 2002 and welcomed Hazel and Finn (short for Phinnaeus) in November 2004.

In May, Roberts told David Letterman of the twins: "They seem to really love each other...He's sort of very boyish and masculine. He has red hair and big green eyes. And she's very girlish and has very blonde hair and blue eyes. He likes blueberries. She likes her daddy."

After the twins were born, Roberts did voice work in two kid-friendly films, the animated Ant Bully and Charlotte's Web, out now. This spring, she made her Broadway debut in the drama Three Days of Rain.

In the fall, she was back to filming in earnest, arriving in Morocco in October to shoot the drama Charlie Wilson's War – with her 23-month-old twins and Moder in tow. She celebrated her 39th birthday at a local restaurant on Oct. 28 and was often seen sightseeing with her clan.

For Roberts, motherhood is her top priority. "The kids bring her such a sense of fulfillment and joy," Roberts's longtime friend and Three Days of Rain producer Marc Platt told PEOPLE in April. "It's wonderful to see."